BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Rhamnus californica | California Coffeeberry 



GENERAL BOTANICAL CHARACTERISTICS : 
California coffeeberry is a native, broad-leaved, sclerophyllous shrub
[13,63,74].  Growth habit varies according to subspecies with plants
ranging from low, spreading shrubs to upright, arborescent individuals
[52].  On favorable sites along the coast, California coffeeberry
occasionally grows as a small tree, reaching heights of approximately 20
feet (6.1 m) [45].  More often, however, it grows as a 4 to 6 foot
(1.2-1.8 m) tall shrub [63].  Bark of young twigs is usually reddish;
older branches have gray, brown, or reddish bark [12,52].  The small,
pinnately veined, evergreen leaves are commonly dark green above and
paler beneath, and are arranged alternately on the stem [53].  Leaf
margins are typically inrolled [12,14].  When growing on xeric sites,
leaves tend to be small and thick; in moist situations they are
relatively large and thin [63].  The inconspicuous, bisexual flowers are
green and occur in small, axillary clusters [53].  The fruit is a juicy,
berrylike drupe approximately 0.25 inch (7-9 mm) in diameter and may be
either green, black, or red in color [34,52].  Berries contain two
smooth, nutlike seeds which closely resemble the commercial coffee bean
[12,14,34].  Although the root crown may become enlarged in response to
repeated postburn sprouting, this structure is not a lignotuber [38,40].
Longevity of California coffeeberry is estimated at 100 to 200 years
[39].


RAUNKIAER LIFE FORM : 
   Phanerophyte


REGENERATION PROCESSES : 
California coffeeberry regenerates by both sexual and vegetative means.
On chaparral sites in southern California, California coffeeberry
maintains itself primarily through sprouting [41].  Seedling
establishment is never very abundant and is restricted to stands of
mature chaparral [39,40,41].  Little or no seedling establishment occurs
immediately following fire [38,40,41].  However, seemingly different
establishment patterns have been observed in other communities [63,66]

Vegetative regeneration:  In the absence of fire, many long-lived
sprouters within stands of mature chaparral rejuvenate their canopies by
continually producing new sprouts from established rootcrowns [40,42].
Generalized information indicates that California coffeeberry may also
maintain itself in this manner [40].  Following disturbances such as
fire or cutting, California coffeeberry sprouts from surviving
adventitious buds on the rootcrown [36,62].

Seed reproduction:  Onset of seed production occurs early in California
coffeeberry, usually by 2 to 3 years of age [19].  Seeds are dispersed
in the fall [41].  Significant, widespread dispersal of the pea-sized
berries occurs through animals, particularly birds [10,41].  Bird
harvest of the fruit crop is often so complete that relatively few seeds
fall beneath the parent plant.  The seeds of California coffeeberry are
apparently quite short lived.  When dried at room temperature, viability
is retained for no longer than 9 months.  At the time of dispersal, each
seed exhibits a chlorophyllous cotyledon, indicating that germination is
imminent [41].  If kept too moist prior to germination, seeds are prone
to rot [19].  Germination occurs readily under favorable moisture and
temperature conditions [34,41].  Keeley [41] recently studied the
germination requirements of California coffeeberry using seed samples
collected in southern California.  After a 1-month stratification at 41
degrees F (5 degrees C), 65 percent of California coffeeberry seeds
germinated when light incubated at 73 degrees F (23 degrees C) for 3
weeks.  Rate of germination was rapid with more than 75 percent of
germination occurring during the first week.  Addition of charate
(powdered charred wood) greatly reduced germination under similar
conditions (15% germination); in the dark, however, addition of charate
stimulated germination relative to the control (90% germination).  In
this study, heat treatments generally decreased germination.  Longer
heating at low temperatures was more detrimental than short bursts of
high temperature [41].  Sampson [62] found that heat treatments produced
a slight increase in germination.

Keeley [38,39,40,41] reported that buckthorns (Rhamnus spp.) are
obligate sprouters after fires in southern California chaparral and
included both California coffeeberry and redberry (Rhamnus crocea)
within this grouping.  Obligate sprouting species are restricted to
sprouting following fire and do not establish seedlings in the initial
postburn environment.  In fact, seedling establishment of obligate
sprouters is always quite limited and follows the generalized scenario
presented below [40,41,71,72]:

     -- Seedlings are established primarily in mature chaparral 
        in gaps resulting from the death of senescing, shorter-lived
        species.
     -- Seedling establishment is often episodic and coincides with
        periods of above normal rainfall .
     -- Although initial establishment may occur in burned or 
        unburned stands during very wet years, continued survival is
        favored beneath mature stands on sites that are relatively
        mesic (north slopes) and which possess a well-developed litter
        layer.
     -- Long-term survival beneath mature chaparral is rare; seedlings
        are stunted and are subjected to heavy browsing by small
        mammals.
     -- Seedlings are most common in very old stands (60 to 100+
        years) where long fire free intervals allow for the build 
        up of seedling populations.

Redberry tends to follow the above pattern [28,29,31,32,42,57], but data
is scant concerning the seedling ecology of California coffeeberry.  A
review of the literature found no data on California coffeeberry
seedling establishment within southern California chaparral.  On Coast
Range sites in northern California, Sampson [62] did not observe any
California coffeeberry seedlings beneath stands of manzanita-ceanothus
(Arctostaphylos spp.-Ceanothus spp.) chaparral.  Seedlings were present
on adjacent burns.  Densities equalled 4,400 seedlings/acre (10,872
seedlings/ha) 1 year after fire; 4 years later, there were approximately
2,300 seedlings/acre (5,683 seedlings/ha).  Precipitation was apparently
below normal during the first three postburn growing seasons [62].
Pelton [58] found occasional California coffeeberry seedlings beneath
mixed-hardwood forests in the Santa Cruz Mountains.  Seedlings of var.
occidentalis apparently require some shade during the establishment
period [19].


SITE CHARACTERISTICS : 
California coffeeberry exhibits a wide ecological amplitude.  Sites
include dry flats, moist slopes, ravines, and rocky ridges, usually at
elevations below 5,500 feet (1,677 m) [52,63].  Soils are typically dry
and well drained [74].  Established plants tolerate full sun to moderate
shade [13,74].

In the Siskiyou Mountains, sites supporting tanoak/coffeeberry plant
associations occur on flat, lower slope positions at elevations ranging
from 1,040 to 3,460 feet (317 to 1,055 m) on southerly aspects;
ultrabasic soils reach depths of approximately 30 inches (76 cm).


SUCCESSIONAL STATUS : 
California coffeeberry is a long-lived and moderately shade-tolerant
shrub that is highly persistent within chaparral, hardwood woodland, and
open conifer forests [13,39].  During extended fire free-intervals,
California coffeeberry is able to outlive, overtop, and shade out many
shorter-lived species [71].  As a component of relatively open canopied
stands, plants persist until the next fire occurs [36,66], at which time
resprouted individuals become part of the initial postburn vegetation
[66].  Griffin [75], however, observed many senescing plants of
California coffeeberry on mixed hardwood sites in the southern Coast
Range; according to Griffin, California coffeeberry had been the
dominant shrub on these sites for quite some time.  Shrubs with
bird-dispersed seed, such as California coffeeberry, have apparently
increased in abundance on relic oak savanna sites in central California
[35].



SEASONAL DEVELOPMENT : 
California coffeeberry typically flowers from April to June [34,52].
Fruit ripening commonly occurs from July through November with dispersal
taking place during the fall [34,41,74].  Immature fruits are green,
turning red or reddish-black when fully ripened [53,63].  Although an
evergreen species, California coffeeberry produces at least some new
leaves each year [23].  Observations on the phenological development of
California coffeeberry during 1936 for sites in Shasta County,
California, are presented below [62]:

    Phenological stage                           Date

    Leaves half developed                        April 11
    Leaves fully developed                       May 16
    Leaves fully developed & fruit forming       June 24

Related categories for Species: Rhamnus californica | California Coffeeberry